time is in ms (10^-3 s)

before_magma: before this PR with magma
after_3: same as those in the parent directory [this PR]
after_3x: after_3 + at::parallel_for with grain size _batch_size / 4 + 1
after_3x_taskset_c4: benchmark after_3x with taskset -c 0,1,2,3 python svdprof.py

shape	cpu	before_magma	after_3	after_3x	after_3x_taskset_c4
[] 2 torch.float32	0.021	2.586	0.238	0.239	0.223
[] 4 torch.float32	0.027	2.116	0.417	0.364	0.337
[] 8 torch.float32	0.033	2.060	0.514	0.454	0.444
[] 16 torch.float32	0.057	2.090	0.642	0.624	0.577
[] 32 torch.float32	0.423	2.847	0.654	0.718	0.686
[] 64 torch.float32	1.002	3.358	1.404	1.392	1.417
[] 128 torch.float32	2.274	11.426	3.303	3.281	3.413
[] 256 torch.float32	9.441	39.182	9.202	9.023	9.138
[] 512 torch.float32	49.966	91.212	25.748	25.772	25.588
[] 1024 torch.float32	175.260	263.738	92.043	92.476	90.484
[1] 2 torch.float32	0.024	2.212	0.222	0.231	0.206
[1] 4 torch.float32	0.027	2.218	0.342	0.336	0.377
[1] 8 torch.float32	0.033	2.225	0.454	0.463	0.382
[1] 16 torch.float32	0.058	2.262	0.589	0.588	0.569
[1] 32 torch.float32	0.326	3.012	0.711	0.699	0.693
[1] 64 torch.float32	0.754	3.454	1.397	1.399	1.366
[1] 128 torch.float32	2.270	11.665	3.308	3.319	3.305
[1] 256 torch.float32	9.648	39.175	9.196	9.116	9.023
[1] 512 torch.float32	48.787	90.463	25.379	25.264	25.380
[1] 1024 torch.float32	167.891	260.806	91.410	92.560	90.867
[2] 2 torch.float32	0.028	4.363	0.097	0.117	0.091
[2] 4 torch.float32	0.036	4.378	0.135	0.174	0.132
[2] 8 torch.float32	0.046	4.409	0.201	0.222	0.190
[2] 16 torch.float32	0.094	4.448	0.284	0.318	0.283
[2] 32 torch.float32	0.566	6.014	0.383	0.396	0.362
[2] 64 torch.float32	1.497	6.953	2.653	2.819	1.928
[2] 128 torch.float32	4.414	23.353	6.660	5.684	4.324
[2] 256 torch.float32	18.673	77.876	18.161	16.171	11.325
[2] 512 torch.float32	111.194	182.043	51.057	40.160	32.993
[2] 1024 torch.float32	354.575	518.680	184.945	168.596	130.100
[4] 2 torch.float32	0.028	8.662	0.091	0.091	0.091
[4] 4 torch.float32	0.041	8.691	0.155	0.149	0.149
[4] 8 torch.float32	0.069	8.708	0.198	0.198	0.189
[4] 16 torch.float32	0.168	8.862	0.288	0.285	0.280
[4] 32 torch.float32	1.095	12.045	0.379	0.386	0.378
[4] 64 torch.float32	3.365	13.926	5.277	5.084	3.649
[4] 128 torch.float32	9.247	48.044	12.925	12.820	9.140
[4] 256 torch.float32	37.481	156.477	36.478	34.047	22.208
[4] 512 torch.float32	213.754	361.161	101.613	89.990	65.715
[8] 2 torch.float32	0.035	17.208	0.095	0.092	0.092
[8] 4 torch.float32	0.063	17.270	0.154	0.153	0.150
[8] 8 torch.float32	0.114	17.357	0.203	0.195	0.191
[8] 16 torch.float32	0.315	17.583	0.293	0.284	0.282
[8] 32 torch.float32	1.992	24.059	0.383	0.384	0.380
[8] 64 torch.float32	5.854	28.145	10.514	9.993	6.117
[8] 128 torch.float32	18.265	94.923	25.795	23.078	13.779
[8] 256 torch.float32	95.982	310.328	72.990	61.663	37.122
[16] 2 torch.float32	0.049	34.331	0.095	0.108	0.093
[16] 4 torch.float32	0.098	34.481	0.152	0.153	0.149
[16] 8 torch.float32	0.208	34.640	0.201	0.197	0.193
[16] 16 torch.float32	0.611	35.079	0.291	0.296	0.290
[16] 32 torch.float32	3.968	48.261	0.382	0.387	0.380
[16] 64 torch.float32	11.263	56.101	21.038	20.856	10.027
[16] 128 torch.float32	37.188	192.676	51.828	41.670	20.302
[32] 2 torch.float32	0.071	69.626	0.095	0.093	0.109
[32] 4 torch.float32	0.166	69.866	0.157	0.154	0.150
[32] 8 torch.float32	0.397	70.369	0.202	0.195	0.193
[32] 16 torch.float32	1.190	71.463	0.292	0.290	0.281
[32] 32 torch.float32	8.144	99.582	0.390	0.384	0.380
[32] 64 torch.float32	22.854	113.871	42.007	39.415	19.829
[64] 2 torch.float32	0.120	137.396	0.110	0.110	0.109
[64] 4 torch.float32	0.306	137.583	0.161	0.153	0.150
[64] 8 torch.float32	0.769	138.404	0.200	0.195	0.198
[64] 16 torch.float32	2.376	139.894	0.325	0.293	0.289
[64] 32 torch.float32	16.032	194.467	0.415	0.384	0.381
[128] 2 torch.float32	0.217	282.373	0.119	0.097	0.110
[128] 4 torch.float32	0.595	281.186	0.176	0.170	0.166
[128] 8 torch.float32	1.515	279.936	0.226	0.236	0.217
[128] 16 torch.float32	4.729	283.615	0.324	0.322	0.322
[256] 2 torch.float32	0.404	553.846	0.136	0.138	0.143
[256] 4 torch.float32	1.162	550.992	0.250	0.243	0.241
[256] 8 torch.float32	3.013	553.561	0.373	0.360	0.368
[512] 2 torch.float32	0.787	1097.264	0.177	0.171	0.170
[512] 4 torch.float32	2.294	1099.425	0.394	0.383	0.381
[1024] 2 torch.float32	1.538	2184.490	0.255	0.262	0.259